JP2018157529A - Image formation apparatus, image formation system and calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable performing appropriate calibration even when printing is performed for a variety of recording medium.SOLUTION: An image formation apparatus comprises: an inline sensor 430 that generates first color information from a density correction pattern formed on a recording medium; a color conversion unit 440 that converts the first color information into second color information; an acquisition unit 325 that acquires spectroscopic information of a density correction pattern by an external colorimetry device 200 when a type of density conversion information of a recording medium, in which the density correction pattern is formed, is not stored; a first density conversion unit 326 that converts the spectroscopic information into density information; a density conversion information generation unit 327 that generates the type of density conversion information of the recording medium, in which the density correction pattern is formed, by associating the second color information with the density information; a second density conversion unit 324 that converts the second color information into the density information using the density conversion information; and a correction curve generation unit 313 that generates correction curve information on the basis of the density information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus, an image forming system, and a calibration method.

  2. Description of the Related Art Conventionally, in an image forming apparatus, a technique called calibration is used in order to keep a change in gradation characteristics caused by a change in environment and a change in device characteristics constant. Examples of calibration types include manual calibration and automatic calibration.

  In manual calibration, a user manually measures a density correction pattern generated by the image forming apparatus using an external colorimetric device, converts the colorimetric density correction pattern into density information, and based on the converted density information. A correction curve is generated, and gradation correction of an image to be printed is performed using the generated correction curve.

  In automatic calibration, the density correction pattern generated by the image forming apparatus is automatically read using an in-line sensor built in the image forming apparatus, and the read density correction pattern is converted into density information using density conversion information. In other words, a correction curve is generated based on the converted density information, and gradation correction of an image to be printed is performed using the generated correction curve (see, for example, Patent Document 1).

  Generally, in an image forming apparatus used for printing that requires color stability and high definition such as commercial printing, the number of times of calibration is increased in order to maintain color stability (execution interval). Tend to be shorter). For this reason, such an image forming apparatus often employs automatic calibration that can reduce the number of work steps as compared with manual calibration.

  By the way, in the image forming apparatus as described above, it is assumed that printing is performed on a wide variety of recording media. However, when automatic calibration is employed, it is necessary to prepare density conversion information for each recording medium. There is.

  However, it is practically difficult to prepare density conversion information in advance assuming a recording medium that is actually used for printing, and printing may be performed using an unintended recording medium. There is also. For this reason, the image forming apparatus as described above may not be able to perform appropriate calibration when printing is performed on a wide variety of recording media.

  The present invention has been made in view of the above circumstances, and an image forming apparatus, an image forming system, and a calibration capable of executing appropriate calibration even when printing is performed on a wide variety of recording media. The purpose of this is to provide a method.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to an aspect of the present invention includes an image forming unit that forms a density correction pattern on a recording medium, and a density correction pattern formed on the recording medium. A reading unit that generates first color information, a color conversion unit that converts the first color information into second color information, and density conversion that stores density conversion information for each type of recording medium An information storage unit, a determination unit that determines whether or not density conversion information of the type of the recording medium on which the density correction pattern is formed is stored in the density conversion information storage unit, and the density correction pattern is formed When density conversion information of the type of the recording medium is not stored in the density conversion information storage unit, an acquisition unit that acquires spectral information that is a color measurement result of the density correction pattern by an external color measurement device; and the spectral information concentration Density conversion information for generating density conversion information of the type of the recording medium on which the density correction pattern is formed, by associating the first density conversion unit that converts the information into the information, the second color information, and the density information A generation unit, a second density conversion unit that converts the second color information into the density information using the generated density conversion information, and a correction that generates correction curve information based on the density information A curve generation unit.

  According to the present invention, even when printing is performed on a wide variety of recording media, there is an effect that appropriate calibration can be executed.

FIG. 1 is a block diagram showing an example of the configuration of the image forming system of the present embodiment. FIG. 2 is a flowchart showing an example of the flow of the procedure of automatic calibration processing performed in the image forming system of the present embodiment. FIG. 3 is a diagram illustrating an example of a reading state of the density correction pattern by the inline sensor of the present embodiment. FIG. 4 is a diagram showing an example of the arrangement of each patch constituting the density correction pattern of the present embodiment. FIG. 5 is a diagram showing an example of the reading order of each patch constituting the density correction pattern by the inline sensor of the present embodiment. FIG. 6 is an explanatory diagram of an example of an arrangement method of each patch constituting the density correction pattern. FIG. 7 is an explanatory diagram of an example of an arrangement method of each patch constituting the density correction pattern. FIG. 8 is an explanatory diagram illustrating an example of a color conversion method of the color conversion unit according to the present embodiment. FIG. 9 is a diagram illustrating an example of density conversion information according to the present embodiment. FIG. 10 is a diagram illustrating an example of density conversion information according to the present embodiment. FIG. 11 is an explanatory diagram of an example of the density conversion method of the second density conversion unit of the present embodiment. FIG. 12 is a schematic diagram illustrating an example of a correspondence relationship between RGBY data and CMYK data in the density conversion information of the present embodiment. FIG. 13 is a detailed diagram illustrating an example of a correspondence relationship between RGBY data and CMYK data in the density conversion information of the present embodiment. FIG. 14 is an explanatory diagram illustrating a detailed example of density conversion information generation processing according to the present embodiment. FIG. 15 is a diagram illustrating an example of the arrangement of the patches constituting the density correction pattern of the first modification. FIG. 16 is a diagram illustrating an example of the reading order of each patch constituting the density correction pattern by the inline sensor according to the first modification. FIG. 17 is an explanatory diagram of the difference between the reading order of the patches constituting the density correction pattern by the inline sensor of Modification 1 and the colorimetric order of the patches constituting the density correction pattern by the external colorimetry device. . FIG. 18 is a flowchart illustrating an example of a flow of a procedure for sorting RGBY data performed in the image forming system 1 according to the first modification. FIG. 19 is an explanatory diagram of an example of an arrangement method of each patch constituting the density correction pattern of the second modification.

  Hereinafter, embodiments of an image forming apparatus, an image forming system, and a calibration method according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an example of the configuration of the image forming system 1 of the present embodiment. As shown in FIG. 1, the image forming system 1 includes an image forming apparatus 10, a PC (Personal Computer) 100, and an external colorimetric apparatus 200.

  The image forming apparatus 10 and the PC 100 are connected via a LAN (Local Area Network) 2, and the external colorimetric apparatus 200 is directly connected to the PC 100. However, the connection form of the image forming apparatus, the PC 100, and the external colorimetric apparatus 200 is not limited to this, and may be connected through an arbitrary network, for example.

  The external color measurement device 200 measures the density correction pattern, and the user manually measures the density correction pattern by using the external color measurement device 200.

  The PC 100 acquires spectral information that is a color measurement result of the density correction pattern from the external color measurement device 200 and transmits the spectral information to the image forming device 10 or transmits print data including an image to be printed to the image forming device 10. To do.

  The image forming apparatus 10 executes printing based on the print data transmitted from the PC 100 or performs calibration. In the present embodiment, the case where the image forming apparatus 10 is a printing apparatus will be described as an example, but the present invention is not limited to this.

  The image forming apparatus 10 includes an engine 400 and a DFE (Digital Front End) 300 that controls the engine 400. In the present embodiment, an example in which the image forming apparatus 10 includes the DFE 300 will be described. However, the present invention is not limited to this, and the DFE 300 may be realized as an apparatus different from the image forming apparatus 10. That is, the image forming apparatus 10 does not have the DFE 300 as an essential configuration.

  The DFE 300 includes a print control unit 310 and a calibration control unit 320. The print control unit 310 includes an I / F 311, a rasterization unit 312, a correction curve generation unit 313, a correction unit 314, and a correction curve storage unit 315. The I / F 311, the rasterization unit 312, the correction curve generation unit 313, and the correction unit 314 may be realized in software by a CPU (Central Processing Unit) or the like, or may be hardware such as an IC (Integrated Circuit). You may implement | achieve and you may implement | achieve combining both together. The correction curve storage unit 315 can be realized by, for example, an HDD (Hard Disk Drive).

  The calibration control unit 320 includes an I / F 321, a density conversion information storage unit 322, a determination unit 323, a second density conversion unit 324, an acquisition unit 325, a first density conversion unit 326, and a density conversion. An information generation unit 327. The I / F 321, the determination unit 323, the second density conversion unit 324, the acquisition unit 325, the first density conversion unit 326, and the density conversion information generation unit 327 may be realized by software such as a CPU, for example. However, it may be realized by hardware such as an IC, or may be realized by using both together. The density conversion information storage unit 322 can be realized by, for example, an HDD.

  The engine 400 includes an image forming unit 410, a sensor control unit 420, an inline sensor 430 (an example of a reading unit), a color conversion unit 440, and an I / F 450. The sensor control unit 420, the color conversion unit 440, and the I / F 450 may be implemented by software such as a CPU, hardware such as an IC, or a combination of both. May be.

  FIG. 2 is a flowchart showing an example of the flow of the procedure of automatic calibration processing performed in the image forming system 1 of the present embodiment.

  First, the engine 400 is adjusted to be in an optimal state (step S10). Specifically, engine 400 sets the maximum density of engine characteristics by engine adjustment. Thereby, the gradation of the image output from the image forming apparatus 10 can be stabilized, and the gradation difference for each printing is reduced.

  Subsequently, the image forming unit 410 of the engine 400 forms (prints) the density correction pattern 500 on the recording medium (step S20). Specifically, the image forming unit 410 irradiates a light beam from an exposure device to form a toner image corresponding to each toner on a photoconductor, and transfers the toner image to a recording medium. Form.

  Examples of the density correction pattern 500 include a pattern in which patches of a plurality of colors (for example, patches of CMYK colors) are arranged, but is not limited thereto. Examples of the recording medium include, but are not limited to, recording paper. For example, images such as coated paper, cardboard, OHP (Overhead Projector) sheet, plastic film, prepreg, and copper foil can be recorded. Any medium may be used.

  Subsequently, the in-line sensor 430 of the engine 400 reads the density correction pattern 500 (color of each patch) formed on the recording medium under the control of the sensor control unit 420 and generates first color information (step) S30). In the present embodiment, the case where the first color information is color information (RGB data) in the RGB color space will be described as an example, but the present invention is not limited to this.

  The density correction pattern 500 formed on the recording medium is read by the in-line sensor 430 and then fixed by overheating and pressurization at a temperature within a predetermined range by the fixing device. The paper is ejected.

  FIG. 3 is a diagram illustrating an example of a reading state of the density correction pattern 500 by the inline sensor 430 of the present embodiment, and FIG. 4 illustrates an example of an arrangement of each patch constituting the density correction pattern 500 of the present embodiment. FIG.

  As shown in FIG. 3, since the in-line sensor 430 reads the density correction pattern 500 being conveyed with high accuracy, the density correction pattern 500 being conveyed is moved up and down by both roller pairs upstream and downstream in the conveyance direction. The density correction pattern 500 is read while being sandwiched and stable. When the inline sensor 430 reads the density correction pattern 500 in an unstable state, the reading value is blurred, and a stable result cannot be obtained.

  For this reason, the front and rear areas in the conveyance direction of the density correction pattern 500 are areas that cannot be read in a state where they are sandwiched up and down by both roller pairs upstream and downstream in the conveyance direction. Therefore, as shown in FIG. 4, it becomes a patch placement prohibited area where the placement of patches is prohibited.

  FIG. 5 is a diagram showing an example of the reading order of each patch constituting the density correction pattern 500 by the inline sensor 430 of the present embodiment. As shown in FIG. 5, the in-line sensor 430 reads each patch constituting the density correction pattern 500 in the order of arrows 510 (from left to right and from top to bottom with respect to the transport direction). This reading order is the same order as the measurement order when the user manually measures the density correction pattern 500 using the external colorimetric device 200.

  FIG. 6 is an explanatory diagram of an example of an arrangement method of each patch constituting the density correction pattern 500, and shows a method of arranging patches of the same color and the same gradation over a plurality of pages. In the present embodiment, the density correction pattern 500 is composed of a plurality of pages. In the example shown in FIG. 6, a cyan (C1) patch and a magenta (M1) patch are applied to each page constituting the density correction pattern 500. It is arranged. In the present embodiment, as shown in FIG. 6, calibration in consideration of color fluctuations in the main scanning direction and the sub-scanning direction in the engine 400 by randomly arranging patches of the same color and the same gradation on a plurality of pages. Is possible.

  FIG. 7 is an explanatory diagram of an example of an arrangement method of each patch constituting the density correction pattern 500, and shows a method of causing patches of the same color and the same gradation to vary with respect to the photoconductor in the sub-scanning direction. . When patches of the same color and the same gradation are varied in the sub-scanning direction, the position in the sub-scanning direction on each page is not varied, but the sub-scanning on the photosensitive member is performed as shown in FIG. Arrange so that the position in the direction can vary.

  For example, as shown in FIG. 7, when a certain patch is arranged at a position corresponding to point A on the photoreceptor, a patch having the same color and the same gradation as the certain patch is located farthest from point A. It is arranged at a position corresponding to point B (in the opposite position).

  Returning to FIG. 2, the color conversion unit 440 converts the first color information (read value of the inline sensor 430) generated by the inline sensor 430 into second color information (step S <b> 40). In the present embodiment, the case where the second color information is color information (RGBY data 411) in the RGBY color space will be described as an example, but the present invention is not limited to this.

  FIG. 8 is an explanatory diagram illustrating an example of a color conversion method of the color conversion unit 440 according to the present embodiment. As illustrated in FIG. 8, the color conversion unit 440 converts the RGB data that is the first color information into the second color data using the color conversion reference parameters that are LUTs (Look Up Tables) created based on the reference paper. It converts to RGBY data 411 which is color information. Therefore, the RGBY data 411 is sRGB data for the reference paper.

  By this color conversion, the device characteristics of the in-line sensor 430 (individual difference of the in-line sensor 430) can be absorbed on the engine 400 side, so the DFE 300 side is conscious of the device characteristics of the in-line sensor 430 (individual difference of the in-line sensor 430) ( Need to be absorbed). The reason why the color conversion unit 440 uses the LUT created based on the reference paper is that, on the engine 400 side, the storage capacity is generally large enough to have an LUT for converting RGB data to RGBY data for each recording medium. This is because there is no room.

  The engine 400 transmits RGBY data 411 that is second color information converted by the color conversion unit 440 to the DFE 300 via the I / F 450 and the I / F 321 of the DFE 300.

  The density conversion information storage unit 322 stores density conversion information. The density conversion information is an LUT for converting the RGBY data 411 that is the second color information transmitted from the engine 400 into density information. In the present embodiment, the case where the density information is CMYK data will be described as an example, but the present invention is not limited to this.

  FIG. 9 is a diagram illustrating an example of density conversion information according to the present embodiment. As shown in FIG. 9, the density information is a one-dimensional LUT for converting input RGBY data 411 into CMYK data according to a γ curve. Specifically, the density information is γ-converted into the corresponding CMYK data using the 4096 gradation CMYK data set in the γ curve (γ table).

  In the present embodiment, the density conversion information storage unit 322 stores density conversion information (LUT) for each type of recording medium, as shown in FIG. In the example illustrated in FIG. 10, the density conversion information storage unit 322 includes density conversion information A for paper A, density conversion information B for paper B, density conversion information C for paper C, and density conversion information for paper D. D is stored.

  Returning to FIG. 2, the determination unit 323 determines whether or not density conversion information of the type of the recording medium on which the density correction pattern is formed is stored in the density conversion information storage unit 322 (step S50).

  When the density conversion information of the type of the recording medium on which the density correction pattern is formed is stored in the density conversion information storage unit 322 (Yes in step S50), the second density conversion unit 324 uses the density conversion information. Then, the second color information is converted into density information (density information is calculated from the second color information) (step S60).

  FIG. 11 is an explanatory diagram illustrating an example of a density conversion method of the second density conversion unit 324 according to the present embodiment. As shown in FIG. 11, the second density conversion unit 324 uses the density conversion information (one-dimensional LUT) of the type of the recording medium on which the density correction pattern is formed, and performs RGBY data as the second color information. 411 is converted into CMYK data which is density information. Since the density conversion information is a one-dimensional LUT, and the RGBY data 411 is also 12 bits for each color, the CMYK data is also 12 bits for each color.

  Returning to FIG. 2, the correction curve generation unit 313 generates correction curve information based on the density information converted by the second density conversion unit 324 (step S70) and stores the correction curve information in the correction curve storage unit 315 (step S70). S80).

  On the other hand, when the density conversion information of the type of the recording medium on which the density correction pattern is formed is not stored in the density conversion information storage unit 322 (No in step S50), the user manually uses the external colorimetric device 200 to density. Color measurement is performed on the correction pattern 500 (step S51). Note that the order of measuring the patches constituting the density correction pattern 500 at this time is the same as the order of reading by the inline sensor 430.

  Subsequently, the acquisition unit 325 acquires spectral information that is a color measurement result of the density correction pattern 500 by the external color measurement device 200 (step S52). Specifically, since the spectral information that is the color measurement result of the density correction pattern 500 is transmitted from the external color measurement device 200 to the PC 100, the acquisition unit 325 transmits the spectral information from the PC 100 via the LAN 2 and the I / F 321. Get information.

  Subsequently, the first density conversion unit 326 converts the spectral information acquired by the acquisition unit 325 into density information (step S53).

  Subsequently, the density conversion information generation unit 327 associates the RGBY data 411, which is the second color information transmitted from the engine 400, with the CMYK data, which is the density information converted from the spectral information, for each patch (step) S54), density conversion information of the type of the recording medium on which the density correction pattern 500 is formed is generated and stored (registered) in the density conversion information storage unit 322 (step S55). In this embodiment, since a plurality of patches of the same color and the same gradation are arranged in the density correction pattern 500, the density conversion information generation unit 327 sets values for patches of the same color and the same gradation. Use after averaging.

  FIG. 12 is a schematic diagram showing an example of the correspondence between RGBY data and CMYK data in the density conversion information of this embodiment. FIG. 13 shows the correspondence between RGBY data and CMYK data in the density conversion information of this embodiment. It is detail drawing which shows an example of a relationship.

  As shown in FIG. 12, the density conversion information corresponds to each plate. Also, the order of arrangement of the read values of the patches and the colorimetric values of the patches differs between the RGBY data and the CMYK data. For this reason, as shown in FIG. 13, the density conversion information generation unit 327 performs sort processing in order of patch gradation values for each CMYK with reference to the patch coordinate data that is the patch position on the density correction pattern 500. Thus, the RGBY data 411 and the CMYK data are associated with each patch to generate density conversion information.

  FIG. 14 is an explanatory diagram illustrating a detailed example of density conversion information generation processing according to the present embodiment. As described with reference to FIG. 13, the density conversion information generation unit 327 associates the RGBY data 411 with the CMYK data by sorting in order of the tone values of the patches for each CMYK, and corresponds from paper white to paper. A density conversion information value by spline interpolation is generated up to the spline interpolation density. The density conversion information generation unit 327 also performs spline interpolation for a set value between the maximum density of each CMYK value and the density corresponding to paper-based spline interpolation. The default setting value can be set by determining the optimum value for each model by evaluating the engine characteristics of the actual machine and the variation in the reading value of the inline sensor 420. Also, the density conversion information generation unit 327 does not perform the spline interpolation when the read value of the patch of the density correction pattern 500 is smaller than the density corresponding to the paper-based spline interpolation, and the maximum value is equal to or less than the density corresponding to the paper-based spline interpolation Linear interpolation is performed with the patch indicating the density value. Also, the density conversion information generation unit 327 extrapolates the table setting value by calculating a formula of a straight line passing through the highlight color and the paper white for an area brighter than the paper white. Thereby, density conversion information is generated.

  Returning to FIG. 2, thereafter, the process proceeds to step S <b> 60, and the second density conversion unit 324 converts the second color information into density information using the density conversion information.

  Next, an example of a flow of a printing process performed in the image forming system 1 of the present embodiment will be described.

  First, the DFE 300 receives print data including an image to be printed from the PC 100 via the I / F 311.

  Subsequently, the rasterization unit 312 performs rasterization processing on the image to be printed based on the received print data.

  Subsequently, the correction unit 314 acquires correction curve information for a recording medium on which image formation is performed in the engine 400 from the correction curve storage unit 315, and is rasterized by the rasterization unit 312 based on the acquired correction curve information. Tone correction is performed on the image data.

  Subsequently, the DFE 300 sends the image data on which the gradation correction has been performed by the correction unit 314 to the engine 400, and the image forming unit 410 forms (prints) the image data on a recording medium.

  As described above, according to the present embodiment, for a recording medium for which density conversion information is not prepared, density conversion information is generated, and correction curve information is generated using the generated density conversion information. Even when printing is performed on a recording medium, appropriate calibration can be executed.

(Modification 1)
In the above embodiment, the case where there is one inline sensor 430 has been described as an example, but two or more inline sensors 430 may be provided. For example, in order to reduce costs, inexpensive inline sensors 430-1 and 430-2 may be connected in series.

  FIG. 15 is a diagram showing an example of the arrangement of patches constituting the density correction pattern 600 of the first modification. When the inline sensors 430-1 and 430-2 are connected in series, the central portion is a joint between the inline sensors 430-1 and 430-2, and thus the density correction pattern 600 cannot be read. For this reason, in addition to the front and rear areas in the conveyance direction of the density correction pattern 600, the central area is also a patch placement prohibited area where the placement of patches is prohibited, as shown in FIG.

  FIG. 16 is a diagram illustrating an example of the reading order of each patch constituting the density correction pattern 600 by the inline sensors 430-1 and 430-2 according to the first modification. As shown in FIG. 16, the in-line sensors 430-1 and 430-2 indicate the patches constituting the density correction pattern 600 in the order of arrows 610 (order from left to right and order from top to bottom with respect to the transport direction). Read with. This reading order is the same as the reading order when there is one inline sensor 430 described in the above embodiment, but the user manually measures the density correction pattern 600 using the external colorimetric device 200. The order is different from the measurement order.

  FIG. 17 shows the reading order of the patches constituting the density correction pattern 600 by the inline sensors 430-1 and 430-2 of the first modification, and the colorimetry of each patch constituting the density correction pattern 600 by the external colorimetric device 200. It is explanatory drawing of a difference with an order.

  The reading order of each patch constituting the density correction pattern 600 by the in-line sensors 430-1 and 430-2 is as described with reference to FIG. On the other hand, since the color measurement of each patch constituting the density correction pattern 600 by the external color measurement device 200 is manually performed by the user, if the reading order by the inline sensors 430-1 and 430-2 is the same, the color measurement man-hours Increases, and the burden on the user is large.

  For this reason, in Modification 1, as shown in FIG. 17, the color measurement order of the density correction pattern 600 is the order from left to right and top to bottom with the density correction pattern 600 rotated by 90 °. To do. Thereby, an increase in the colorimetric man-hours can be prevented, and an increase in user burden can also be prevented.

  However, in this case, unlike the above embodiment, the reading order of the density correction pattern 600 is different from the measurement order, and the patches constituting the density correction pattern 600 cannot be dealt with. In Example 1, the reading values (specifically, RGBY data) by the inline sensors 430-1 and 430-2 are sorted.

  FIG. 18 is a flowchart illustrating an example of a flow of a procedure for sorting RGBY data performed in the image forming system 1 according to the first modification.

  First, the density conversion information generation unit 327 acquires RGBY data that is second color information transmitted from the engine 400 (step S101).

  Subsequently, the acquisition unit 325 acquires CMYK data (spectral information) that is a color measurement result of the density correction pattern 600 by the external color measurement device 200 (step S102).

  Subsequently, the density conversion information generation unit 327 deletes patch data unnecessary for sorting from the RGBY data and the CMYK data (step S103).

  Subsequently, the density conversion information generation unit 327 performs rearrangement so that the RGBY data and CMYK data from which unnecessary patch data has been deleted are in the same order (step S104). The rearrangement is performed in ascending order of patches for each CMYK.

  Subsequently, the density conversion information generation unit 327 generates density conversion information by associating the rearranged RGBY data and CMYK data patches (step S105).

(Modification 2)
Patches may be arranged on the density correction pattern 600 so that the user can reduce the number of color measurement steps of the density correction pattern 600 that are manually performed using the external colorimetric device 200.

  FIG. 19 is an explanatory diagram of an example of an arrangement method of each patch constituting the density correction pattern 600 of the second modification. In the colorimetry of each patch constituting the density correction pattern 600 by the external colorimetry device 200, the colorimetric data is regarded as a true value, so that only one measurement is required. For this reason, in the second modification, as shown in FIG. 19, patches necessary for manual measurement are concentrated and arranged on the first page (specifically, the area 620 on the first page). This eliminates the need for the user to perform color measurement on all pages in the color measurement of each patch constituting the density correction pattern 600 by the external color measurement device 200, thereby reducing the number of color measurement steps.

  Note that, as in Modification 2, it may be possible to select whether to measure the color of only some pages or to measure the color of all pages depending on the mode.

(Modification 3)
In the above embodiment, the density correction information may be prepared and generated not only for the type of the recording medium but also for each type and size of the recording medium.

(program)
The program executed in each device of the above embodiment is an installable or executable file, such as a CD-ROM, CD-R, memory card, DVD (Digital Versatile Disk), flexible disk (FD), etc. The program is stored in a computer-readable storage medium and provided.

  Further, the program executed by each device of the above-described embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. Further, the program executed by each device of the above embodiment may be provided or distributed via a network such as the Internet. Further, the program executed by each device of the above embodiment may be provided by being incorporated in advance in a ROM or the like.

  The program executed by each device of the above embodiment has a module configuration for realizing the above-described units on a computer. As actual hardware, for example, the CPU reads out a program from the ROM to the RAM and executes the program, so that each functional unit is realized on the computer.

  The above embodiment is presented as an example, and is not intended to limit the scope of the invention. The above-described novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1 Image forming system 2 LAN
10 Image forming apparatus 100 PC
200 External color measuring device 400 Engine 300 DFE
310 Print Control Unit 311 I / F
312 Rasterization unit 313 Correction curve generation unit 314 Correction unit 315 Correction curve storage unit 320 Calibration control unit 321 I / F
322 density conversion information storage unit 323 determination unit 324 second density conversion unit 325 acquisition unit 326 first density conversion unit 327 density conversion information generation unit 410 image forming unit 420 sensor control unit 430, 430-1, 430-2 inline Sensor 440 Color converter 450 I / F

JP 2008-131618 A

Claims (10)

An image forming unit for forming a density correction pattern on a recording medium;
A reading unit that reads the density correction pattern formed on the recording medium and generates first color information;
A color conversion unit that converts the first color information into second color information;
A density conversion information storage unit that stores density conversion information for each type of recording medium;
A determination unit that determines whether or not density conversion information of a type of the recording medium on which the density correction pattern is formed is stored in the density conversion information storage unit;
When density conversion information of the type of the recording medium on which the density correction pattern is formed is not stored in the density conversion information storage unit, spectral information that is a color measurement result of the density correction pattern by an external color measurement device is acquired. An acquisition unit;
A first density converter that converts the spectral information into density information;
A density conversion information generation unit that associates the second color information with the density information and generates density conversion information of the type of the recording medium on which the density correction pattern is formed;
A second density conversion unit that converts the second color information into the density information using the generated density conversion information;
A correction curve generator for generating correction curve information based on the density information;
An image forming apparatus comprising:   When the density conversion information of the type of the recording medium on which the density correction pattern is formed is stored in the density conversion information storage unit, the second density conversion unit uses the density conversion information to store the second density conversion information. The image forming apparatus according to claim 1, wherein the color information is converted into the density information.   The image forming apparatus according to claim 1, further comprising a correction unit that performs gradation correction based on the correction curve information. The density correction pattern is composed of a plurality of patches,
The image forming apparatus according to claim 1, wherein patches of the same color and the same gradation are arranged over a plurality of pages in the density correction pattern.   5. The image forming apparatus according to claim 4, wherein patches of the same color and the same gradation are arranged in the main scanning direction and the sub-scanning direction in consideration of the period of the photoconductor in the density correction pattern.   5. The image forming apparatus according to claim 4, wherein patches required for color measurement of the density correction pattern by the external color measurement device are collected on the first page of the density correction pattern. The reading unit is configured by connecting a plurality of inline sensors in series,
The image forming apparatus according to claim 1, wherein no patch is arranged in a central region of the density correction pattern. The reading order of the density correction pattern by the reading unit is different from the color measuring order of the density correction pattern by the external colorimetry device,
The density conversion information generation unit rearranges at least one of a value constituting the second color information and a value constituting the density information, and associates the second color information with the density information. 8. The image forming apparatus according to 7. An image forming unit for forming a density correction pattern on a recording medium;
A reading unit that reads the density correction pattern formed on the recording medium and generates first color information;
A color conversion unit that converts the first color information into second color information;
A density conversion information storage unit that stores density conversion information for each type of recording medium;
A determination unit that determines whether or not density conversion information of a type of the recording medium on which the density correction pattern is formed is stored in the density conversion information storage unit;
When density conversion information of the type of the recording medium on which the density correction pattern is formed is not stored in the density conversion information storage unit, spectral information that is a color measurement result of the density correction pattern by an external color measurement device is acquired. An acquisition unit;
A first density converter that converts the spectral information into density information;
A density conversion information generation unit that associates the second color information with the density information and generates density conversion information of the type of the recording medium on which the density correction pattern is formed;
A second density conversion unit that converts the second color information into the density information using the generated density conversion information;
A correction curve generator for generating correction curve information based on the density information;
An image forming system comprising: An image forming step of forming a density correction pattern on a recording medium;
A reading step of reading a density correction pattern formed on the recording medium and generating first color information;
A color conversion step of converting the first color information into second color information;
A determination step of determining whether density conversion information of the type of the recording medium on which the density correction pattern is formed is stored in a density conversion information storage unit;
When density conversion information of the type of the recording medium on which the density correction pattern is formed is not stored in the density conversion information storage unit, spectral information that is a color measurement result of the density correction pattern by an external color measurement device is acquired. An acquisition step;
A first density conversion step for converting the spectral information into density information;
A density conversion information generating step for generating density conversion information of the type of the recording medium on which the density correction pattern is formed in association with the second color information and the density information;
A second density conversion step of converting the second color information into the density information using the generated density conversion information;
A correction curve generating step for generating correction curve information based on the density information;
Calibration method including: